1. Field of the Invention
This invention relates to a continuous process for recovering particulate carbon from synthesis gas, and particularly from carbon-water dispersions.
2. Description of the Prior Art
Raw synthesis gas leaving a partial oxidation synthesis gas generator comprises principally CO and H.sub.2, together with minor amounts of finely divided carbon or particulate carbon. Preferably, the particulate carbon may be removed from the effluent gaseous stream by contacting the gas with water in a quenching and scrubbing zone. The finely divided carbon soot particles are wetted by water so as to form a mixture of particulate carbon and water. The particulate carbon produced in synthesis gas manufacture is unique, and problems associated with the separation of synthesis gas carbon are not the same as those encountered in the removal of carbon or solids made by other processes. For example, the fine carbon particles from partial oxidation are unusual in that they will settle in water to only about 1.0 to 3.0 weight percent, whereas conventional carbon blacks may settle to concentrations of as much as 10 weight percent.
To produce synthesis gas economically, it is important to separate clear water from the carbon-water mixture for reuse. However, the fine particle size of the carbon soot makes ordinary filtration methods difficult and makes gravity separation uneconomical because of excessive settling times, i.e. about 1-2 days. Further, liquid-hydrocarbon extraction procedures for recovering particulate-carbon soot are complex. In a prior process by R. M. Dille, et al, U.S. Pat. No. 3,147,093, a hydrocarbon oil was added to the water-carbon mixture to facilitate separation; but this operation resulted in the formation of soft aggregates of carbon curds contaminated with oil. Further, under some conditions troublesome emulsions which are difficult to separate may form upon the mixing of an oil with the carbon-water dispersion. By the process of our invention, particulate carbon, free from organic matter, is quickly and easily separated from quench and scrubbing water, so as to permit recycle of the clear water.
The oxo process is the commercial application of a chemical reaction called oxonation or, more properly, hydroformylation. In this reaction, hydrogen and carbon monoxide are added across an olefinic bond to produce aldehydes containing one more carbon atom than the olefin.
The oxyl process is a method for directly producing alcohols by catalytically reducing carbon monoxide with hydrogen so as to link several partially reduced carbon atoms together. Essentially it is a modified Fischer-Tropsch Process which preferentially produces oxygenated compounds consisting mainly of alcohols.